Page 274 - Practical English Usage 3ed - Michael Swan, Oxford

immediately, the moment etc: conjunctions 267
267 immediately. the moment etc: conjunctions
In British English, immediately and directly can be used as conjunctions, to mean 'as soon as'.
Tell me immediately you have any news.
I knew something was wrong immediately I arrived. Directly I walked in the door, I smelt smoke.
The moment (that), the instant (that), the second (that) and the minute (that) can be used in the same way (in both British and American English).
Telephone me the moment (that) you get the results. I loved you the instant (that) I saw you.
268 imperatives
1 forms and use
In sentences like Come here, Be quiet, Have a drink or Don't worry about it, the verb forms come, be, have and don't worry are called 'imperatives'. Mfirmative imperatives have the same form as the infinitive without to; negative imperatives are constructed with do not (don't).
Imperatives are used, for example, to tell or ask people to do things, to make suggestions, to give advice or instructions, to encourage and offer, and to express wishes for people's welfare.
Look in the mirror before you drive off. Please do not lean out ofthe window. Tell him you're not free this evening. Try again - you nearly did it.
Have some more tea.
Enjoy your holiday.
An imperative followed by and or or can mean the same as an if-clause.
Walk down our street any day and you'll see kids playing.
(= If you walk ...)
Shut up or I'll lose my temper. (= If you don't shut up ...) Don't do that again or you'll be in trouble.
2 emphatiC imperative: Do sit down
We can make an emphatic imperative with do.
Do sit down. Do be more careful. Do forgive me.
3 passive imperative: get vaccinated
To tell people to arrange for things to be done to them, we often use get + past participle.
Get vaccinated as soon as you can. For more about get as passive auxiliary, see 223.5.
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